Generally, active noise cancellation (ANC) can refer to the process of producing a sound from a speaker to attenuate noise (e.g., an unwanted sound) present in an area. To attenuate the noise, the speaker is configured to produce a sound having a similar amplitude, but opposite phase to the noise. Thus, the sound produced by the speaker will combine with and, due to the superposition of waves, reduce the amplitude of the opposite phase noise.
Generally, there are two methods of accomplishing ANC; feedback (typically analog) and feedforward (typically analog or digital). Feedback solutions include an error (e.g., near-field) microphone located near the speaker that senses the sound after the sound produced by the speaker has combined with the noise. The audio information from the error microphone is sent to a controller which then adjusts the sound produced by the speaker based thereon. In a feedforward solution, a reference (e.g., far-field) microphone senses noise before it combines with the sound produced by the speaker. The audio information from the reference microphone is sent to a controller which causes the speaker to produce a sound having a similar amplitude, but opposite phase to the noise sensed by the reference microphone. Feedforward solutions can be either fixed or adaptive, with adaptive solutions being generally more robust than fixed solutions. Various feedback or feedforward ANC solutions have been used in stereo ANC headsets.